The present invention generally relates to solar energy collecting systems and methods for their use and production. More particularly, this invention relates to solar panels whose construction includes lightweight flat multi-channel tubes, and to solar energy collecting systems that mainly comprise the solar panels and a water tank. The solar panel is capable of achieving improved efficiency so that less collector area will be required to be installed or, for a given collector area, more hot water will be produced.
Existing solar energy thermal collectors are generally available in three forms: formed plastic collectors, flat plate collectors, and evacuated tube collectors. Plastic collectors generally employ polymeric multi-channel tubes or panels directly exposed to the sun for heating a fluid (for example, water) flowing through the channels. Flat plate collectors have typically employed an absorber plate contacted by round copper tubing which are encased together in an insulated enclosure. The absorber plate may be in the form of flat fins between the round tubes. The absorber plate is heated by the sun, and the absorbed heat is conducted through the absorber plate, through the absorber-tube joints, and through the tube walls to a heating fluid flowing through the tubes. Evacuated tube collectors generally employ individual vacuum-sealed glass tubes, each containing a copper tube through which a heating fluid flows. The copper tube is typically contacted by an absorber fin or sheet within the glass tube, and the surrounding vacuum acts as an insulator to minimize heat losses from the copper tube to the environment outside of the glass tube and thereby enable the copper tube to reach higher temperatures.
The thermal collector technologies outlined above have a number of limitations. Liquid flow area within the tubes is small compared to the available absorption area of the absorber plates. Highest efficiencies are only achieved during midday for non-tracking panels. Costs are relatively high, especially for vacuum tubes. Copper tubing is relatively heavy. Polymeric tubes, while not susceptible to corrosion, are prone to distortion and UV degradation and are not capable of withstanding high temperatures. Vacuum tubes are fragile, expensive, and require large amounts of space, and the glass tubes limit the size of the absorber fin or sheet. Finally, the vacuum insulation method employed by vacuum tubes results in an array of tubes occupying a large space, with each glass vacuum tube containing a single copper round tube and a typical glass tube diameter of about 40 mm.